There is known a microparticle sorting device (a flow cytometer, for example) that optically, electrically, or magnetically detects the properties of microparticles such as cells, and separates and collects only microparticles having a designated property.
Cell separation with a flow cytometer involves producing a fluid stream (a flow of droplets) by breaking a cell-containing sample liquid and a sheath liquid into droplets, which are ejected from an orifice formed on a flow cell or a microchip. The breaking of the sample liquid and the sheath liquid into droplets is performed by applying vibration at a designated frequency to the orifice with a vibratory element. The cell-containing droplets are imparted with an electric charge and ejected. By electrically controlling the direction of movement of each droplet, target cells having a desired property, and all other non-target cells, are collected in separate collecting receptacles.
For example, PTL 1 discloses, as a microchip-type flow cytometer, a “device for sorting particles provided with a microchip in which a flow channel through which liquid containing particles is flown and an orifice for discharging the liquid flowing through the flow channel to a space outside the chip are provided, a vibratory element for making and ejecting a droplet of the liquid at the orifice, a charging means for giving charge to the ejected droplet, an optical detecting means for detecting an optical characteristic of the particles flowing through the flow channel, paired electrodes arranged along the direction of movement of the ejected droplet and opposed with the moving droplet therebetween, and two or more vessels for collecting the droplet passing between the paired electrodes.”